共查询到20条相似文献,搜索用时 859 毫秒
1.
本文用CTAB/丁醇/庚烷/水四组分微乳液体系沉淀制备纳米BaF2.研究了体系中丁醇和CTAB的质量比、庚烷质量、含水量及溶质对微乳液体系稳定性和产物BaF2沉淀粒径、分布的影响.稳定的Ba(NO3)2微乳液和NH4F微乳液混合制得10nm的BaF2颗粒,单分散性好,颗粒呈球形.BaF2粒径大小和分布随CTAB和水质量比值的增大而减小. 相似文献
2.
沉淀剂对共沉淀法制备Lu2O3发光粉体形貌的影响 总被引:2,自引:0,他引:2
研究了共沉淀法制备Eu3 掺杂氧化镥(Lu2O3)发光粉体过程中三种不同的沉淀剂(氨水、碳酸氢铵以及NH3·H2O NH4HCO3两者的混合溶液)对所得粉体形貌的影响.通过差热热重质谱联用(DTA-TG-MS)和红外光谱研究了不同沉淀剂所得沉淀前驱体的热分解行为,结合显微结构观察、粒度分布和比表而积测试,对i种沉淀剂影响Lu2O3晶粒尺寸和团聚状态的规律进行了探讨.研究发现:采用NH3·H2O NH4HCO3混合沉淀剂得到的Lu2O3粉体具有最佳的显微结构和粒径分布状态,沉淀前驱体经1000°C煅烧2h,粉体的平均晶粒尺寸为35nm,中位粒径(D50)为0.48μm. 相似文献
3.
4.
改性的沉淀法制备三氧化二钇粉体 总被引:6,自引:0,他引:6
以Y(NO3)3和NH4HCO3为原料,添加适量的表面活性剂(聚乙烯醇)和(NH4)2SO4,利用改性的沉淀法制备了Y2O3前驱体。对前驱体在不同温度下进行焙烧,成功制备了超细Y2O3纳米粉体。分别采用XRD、TEM和TG—DTA分析了不同温度下煅烧所得粉体的物相、形貌以及前驱体热分解特性。结果表明,前驱体在900℃下保温1.5h,得到的Y2O3粉体颗粒近球形,细小均匀,平均尺寸约为7nm,粒径分布极窄,并具有很好的分散性和流动性。 相似文献
5.
6.
《无机材料学报》2010,(10)
以NH4HCO3-NH3·H2O为混合沉淀剂,采用化学共沉淀法制备CaMoO4:Eu3+红色荧光粉.通过TG-DTA和XRD研究CaMoO4:Eu3+前驱体的热分解和晶相形成过程;采用SEM和PL表征了该荧光粉的表面形貌和发光性能,并与NH4HCO3沉淀剂、NH3·H2O沉淀剂合成的CaMoO4:Eu3+荧光粉以及高温固相法制备的荧光粉进行对比.结果表明,煅烧温度700℃时,前驱体能够完全转换成单一CaMoO4:Eu3+白钨矿结构;煅烧温度900℃制备的荧光粉发光强度达到最大值;采用混合沉淀剂制备的荧光粉大小均匀、无团聚、呈类球型,平均粒径0.9μm.与高温固相法比较,其激发光谱中的Eu-O电荷迁移带向长波方向微小移动,而7F0→5L6(394nm)和7F0→5D2(465nm)的强电子吸收能有效改善红色荧光粉使用性能;与单独的NH4HCO3或NH3·H2O沉淀剂或高温固相法相比,该荧光粉发光性能显著改善,发光强度为传统固相法的2倍. 相似文献
7.
以Al粉,TiO2粉,C粉为原料,通过放热弥散法制备Al-TiO2-C细化剂,其中TiO2的粒径分别为30,60,90,200 nm。研究TiO2的粒径对细化剂组织的影响以及不同细化剂对工业纯铝的细化效果。利用XRD,SEM,EDS技术表征不同TiO2粒径制备的Al-TiO2-C细化剂相组成和显微组织。结果表明:Al-TiO2-C细化剂主要由Al3Ti,TiC和Al2O3相组成。TiO2粒径的变化会直接影响第二相的数量、分布与形貌,当TiO2粒径为30~90 nm时,Al-TiO2-C细化剂中Al3Ti和TiC数量多但有明显的偏聚现象,分布不均匀,其中Al3Ti相呈长条状。当TiO2粒径为200 nm时,第二相分布均匀但数量较少,其中Al3Ti相呈块状。添加30 nm TiO2制备的Al-TiO2-C细化剂后,α-Al形核温度由659.4℃上升到661.8℃,再辉温度由1.2℃下降到0.3℃,平均晶粒尺寸最小为633μm,细化效果最佳。 相似文献
8.
9.
10.
化学沉淀法制备纳米氧化铝过程中的防团聚研究 总被引:2,自引:0,他引:2
分别以无水乙醇、去离子水为溶剂,以NH3·H2O、NH4HCO3为沉淀剂,采用化学沉淀法制备了纳米Al2O3粉体.利用TEM、XRD、FT-IR和激光粒度仪研究了溶剂、沉淀剂、浓度、前驱体等因素对纳米Al2O3粉体制备过程中的团聚程度的影响.结果表明:当NH4HCO3和Al(NO3)3水溶液浓度分别为3.0mol/L和0.3mol/L时,借助超声分散和微波干燥,得到的纳米Al2O3粉体粒度均匀、分散良好,1100℃煅烧所得粉体平均粒径为20nm. 相似文献
11.
12.
Effects of Additive AlCl3 on Crystal Phase, Particle Size and Microstructural Parameters of Nanocrystalline TiO2 Prepared by HF-PCVD 总被引:1,自引:0,他引:1
Haiping XU Yanping SUN Department of Chemical Engineering Taiyuan University of Technology Taiyuan China Xinmou CHEN Xinmou New Technique Corporation Shijiazhuang Economic Development Zone Shijiazhuang China 《材料科学技术学报》2004,20(6):641-643
Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable 相似文献
13.
Jingchang ZHANG Qing LI Weiliang CAO Institute of Modern Catalysis The Key Laboratory of Science Technology of Controllable Chemical Reactions Ministry of Education Beijing University of Chemical Technology Beijing China 《材料科学技术学报》2005,21(2):191-195
A series of TiO2-SnO2 nano-sized composite photo-catalysts containing Sn (9.3%-30.1%) were prepared from TiCI4 and SnCl4·5H2O by using sol-gel, supercritical fluid dry and solid-phase reaction (SCFD) combination technology. Characterizations with X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR) showed that, in addition to anatase type TiO2, a new active phase (Ti, Sn)O2 (with particle size of 2.0-4.3 nm) formed, and there were no SnO2 crystals observed in the range of the doping concentration studied. Photo-catalytic reaction of phenol was used as a model reaction to evaluate the catalytic activities of the obtained catalysts. Compared with pure TiO2 or Ti-Sn catalyst prepared with general sol-gel method, Ti-Sn nano-composite photo-catalyst thus obtained showed significant improvement in catalytic activity. The photo-catalytic degradation rate of phenol could reach as high as 93.5% after 7 h. The preparation conditions of the new phase (T 相似文献
14.
TiO2 in commercial sunscreen lotion: flow field-flow fractionation and ICP-AES together for size analysis 总被引:1,自引:0,他引:1
A new method for determining the size of titanium dioxide particles is proposed and assayed in a commercial sunscreen product. Today many sun protection cosmetics incorporate physical UV filters as active ingredients, and there are no official methods for determining these compounds in sunscreen cosmetics. Here flow field-flow fractionation (FlFFF) has been tested, first to sort two different types of TiO2 nano- and microstandard materials (AeroxideTiO2 Degussa P-25 and TiO2 rutile 0.1-0.2-microm size) and then to fractionate TiO2 particles, extracted from a commercial sunscreen lotion. All the TiO2 FlFFF separations were detected by UV but during elution fractions were collected and their Ti content measured by inductively coupled plasma-atomic emission spectrometer (ICP-AES); the Ti concentration profiles obtained by ICP-AES were well correlated with the UV signals. The TiO2 particle mass-size distribution were calculated from the UV profiles. This methodology is relatively simple and rapid, and the sample treatment is as a whole easy and low cost. 相似文献
15.
《Advanced Powder Technology》1999,10(1):37-50
Crystalline, spherical barium titanate fine powders with a narrow particle size distribution were prepared by ultrasonic spray pyrolysis. The stability of the starting solution was influenced by type of barium source and peptizer. The particle structure was influenced by the pyrolysis temperature of the barium source. The particle structure derived from barium acetate was dense, while powders derived from barium nitrate involved a lot of hollow particles. As-prepared powders were crystallized to a perovskite structure. Inductively coupled plasma analysis showed that the BaO/TiO2 molar ratio of as-prepared powders was 50.5:49.5. The effects of the concentration of the starting fluid, pyrolysis temperature and flow rate of carrier air through the furnace on powder characteristics such as particle size, size distribution and crystal phase were investigated. The particle size depended on the concentration of starting solution and the flow rate of carrier air, but the particle size distribution was independent of these variables. Single-phase BaTiO3 was obtained at more than 700°C. The relative density of barium titanate sintered at 1200°C was 98%. The hollow particles in the powders resulted in a low sintering density and a large grain size. The dielectric constant and tan δ of barium titanate at 25°C were 4500 and 0.02, respectively. 相似文献
16.
17.
运用物化相分析对Ti0.07-Mo0.2和Ti0.09-Mo0.2的两种Ti—Mo微合金钢析出相中二相粒子的尺寸、分布频度、质量百分数等进行了定量研究,运用Gleebe-3800热模拟机对Ti0.07~Mo0.2和Ti0.09~Mo0.2和Ti0.058的三种钢进行了应力弛豫试验,研究了二相粒子析出前的孕育时间。结果表明,Ti0.07-Mo0.2和Ti0.09-Mo0.2试验钢中,二相粒子尺寸在36nm以下的质量百分数占绝大。随着Ti含量由0.07%增加到0.09%,尺寸36nm以下的二相粒子的质量百分数增加,二相粒子平均尺寸减小。形核率增大,使得形核孕育时间缩短。Ti0.07-Mo0.2钢和Ti0.058钢相比,由于Mo能够降低了Ti,C,N这些形成元素的活度,推迟其碳氮化物在奥氏体形核,降低了形核率,使得Ti0.058钢的析出时间比Ti0.07-Mo0.2钢缩短。 相似文献
18.
19.
主要讨论了B/TiO2摩尔比对Al-TiO2-B系XD(热扩散反应)合成过程及其力学性能的影响。随着B/TiO2摩尔比从0增加到2,Al基体的晶粒细化,反应产物 Al2O3分布的均匀性提高;棒状物Al3Ti的量逐渐减少直至消失;同时,该反应系的实际燃烧温度下降,反应速度减小,反应产物的致密度提高,力学性能明显改善,其抗拉强度由224.5MPa上升到354.5MPa,延伸率由3.2 %升高到5.6 %,断口中棒状物Al3Ti逐渐消失,形成的韧窝细小而密集。 相似文献
20.
Bhattacharya K Tripathi AK Dey GK Gupta NM 《Journal of nanoscience and nanotechnology》2005,5(5):790-796
Nanosize clusters of titania were dispersed in mesoporous MCM-41 silica matrix with the help of the incipient wet-impregnation route, using an isopropanol solution of titanium isopropoxide as precursor. The clusters thus formed were of pure anatase phase and their size depended upon the titania loading. In the case of low (< 15 wt %) loadings, the TiO2 particles were X-ray and laser-Raman amorphous, confirming very high dispersion. These particles were mostly of < or = 2 nm size. On the other hand, larger size clusters (2-15 nm) were present in a sample with a higher loading of approximately 21 wt %. These particles of titania, irrespective of their size, exhibited an absorbance behavior similar to that of bulk TiO2. Powder X-ray diffraction, N2-adsorption and transmission electron microscopy results showed that while smaller size particles were confined mostly inside the pore system, the larger size particles occupied the external surface of the host matrix. At the same time, the structural integrity of the host was maintained even though some deformation in the pore system was noticed in the case of the sample having highest loading. The core level X-ray photoelectron spectroscopy results revealed a + 4 valence state of Ti in all the samples. A positive binding energy shift and the increase of the width of Ti 2p peaks were observed, however, with the decrease in the particle size of supported titania crystallites, indicative of a microenvironment for surface sites that is different from that of the bulk. 相似文献